Wait...OK, let's think about this.
It's LONG been possible to deliver both barrels of a SxS with double triggers. But that's because you have two triggers, and use two different fingers to set 'em both off at once. You're still doing one trigger pull for one shot. Twice.
So far that's not been classed as NFA.
If this critter is a pump with TWO triggers, shouldn't be a problem. (Well, not legally...tactically, you'd want to set off both barrels before racking it otherwise you spit out live ammo.)
But if the triggers are interlinked...oops, yeah, that sounds NFAish to me.
So, you have to somehow make both triggers accessible to the fingers of one hand, either both at once or in sequence. Which probably explains why the two guns are staggered, so that the triggers are not seriously modded but can still be set off one at a time when desired.